In this opening scene (below), Dexter's car is heading northwest, at around5460 E. Ocean Blvd,while the camera is looking south. The brown beach house, seen on the right, is at5454 Ocean,right next to (northwest of) Deb's beach house:

After Dex hangs up on Vogel's call, the next shot is around5465 E. Ocean, almost the same place
(next to Deb's beach house), but looking the opposite direction. The building on the left is the
U.S. Sailing Center, at 5489 E Ocean Blvd.. The houses on the right side are on 55th Place: